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Medical grade silicone rubber is unlike conventional forms used in the medical industry. Its dozens of features and characteristics surpass expectations, and liquid silicone rubber, or LSR, is the ideal material in manufacturing life science products. Whether you’re searching for small or large, flexible or high durometer products, LSR can accommodate any application in the field.
If your company requires long-term solutions — that actually last an entire lifetime — through high and low temperatures, and that will increase the performance, safety, and comfort of your medical products, liquid silicone rubber from SIMTEC Silicone Parts is your answer. We can create medical grade liquid silicone rubber parts such as diaphragms and syringe stoppers, plus infusion pumps and dialysis filters.
LSR in the life science industry can keep up with the ever-changing demands of product regulations, safety checks, and high standards. SIMTEC continues to perfect our LSR and LSR 2-Shot processes because we know medical experts rely on our expertise to save lives. Our innovative technology and techniques can help propel medical liquid silicone and give your company a competitive advantage.
As you read our e-book, it will help you understand what LSR is, its properties, and how it serves injection molding in the medical industry. SIMTEC professionals implement three different silicone rubber processes and work with you to determine which solutions work best for your application. We produce various medical device LSR parts to suit the needs of doctors, surgeons, and nurses.
SIMTEC also places our rubber through a vulcanization process to create more durable products. And with the cross-linking that occurs during vulcanization, we can develop the most durable rubber on the market. We can craft an endless number of solutions to match your needs — anywhere from seals, gaskets, and O-rings to vibration dampers, connectors, caps, and syringe stoppers. Our technicians manufacture all medical LSR products to fit your particular needs.
Throughout the guide, we provide an extensive list of parts we can create, but the list isn’t limited to our abilities. This guide will help you understand the features of LSR and how liquid silicone rubber can positively affect your products. Further on, we discuss the advantages of using silicone rubber for various medical components. For example, our solutions can withstand extreme temperatures — both hot and cold — and are biocompatible, which is vital in your line of work. Other pros of LSR include it being flexible, UV resistant, and tasteless.
Learning about liquid silicone rubber and how it can advance your company is essential before beginning the process of designing products. SIMTEC will support you each step of the way to ensure you have perfect components and solutions that are compatible with their functions.
Let’s begin with the basics. Liquid silicone rubber or LSR is an odorless, tasteless and hypoallergenic material. LSR is a standard solution used in various industries ranging from medical and food to automotive, household goods, and wearable technology. But for you to learn how it can impact your company, we will start from the beginning.
Liquid silicone rubber is based on silicon dioxide or sand. Silicone has alternating silicon and oxygen molecules, and when they react with methyl chloride, it creates polydimethylsiloxane, also known as PDMS. Silicone has inorganic as well as organic properties, but LSRs are pure with no curing agents, plasticizers, stabilizers, or promoters. Therefore, they are cross-linked or cured through a reaction.
LSR is a two-component material. Component A is the catalyst, and component B is the cross-linking agent. The reaction between both materials induces the curing process, and cross-linking occurs. SIMTEC Silicone Parts can manufacture LSR in a range of grades, types, and properties for dozens of medical rubber parts in the pharmaceutical industry. There are three main steps in creating LSR — mixing, molding, and finishing.
Manufacturing silicone medical products requires special machinery unlike conventional molding with thermoplastics. LSR begins as two separate raw materials — components A and B. Silicon dioxide, or sand, is processed into silicone then reacted with methyl chloride in a 1:1 ratio. Both components A and B are shipped to SIMTEC’s facility in separate containers to prevent the chemical reaction from occurring before arrival.
For us to begin forming LSR, we feed both of the components through high-pressure hoses from drums into a mixing head. During this stage, cold runners keep temperatures below the curing point which helps make sure the silicone remains uncured before reaching the molding cavities. The water-cooled injection barrels are often set between 60 and 100 degrees Fahrenheit.
When mixed in a static mixer, the silicone and methyl chloride begin to react. Once LSR forms, it has a low viscosity which helps it fill each piece of the mold and other small features of your product. It has a pasty consistency similar to peanut butter. Although a low viscosity can lead to flash, our intricate mold designs minimize any occurrences. Different forms of LSR have viscosities ranging from 10,000 to 1,000,000 cps.
The next step involves heating the LSR to initiate the curing process for solidification. Unlike traditional rubber solutions, where heat melts and reforms rubber, heating LSR turns the liquid into a solid. Temperatures range between 355 and 390 degrees Fahrenheit to build LSR, and high clamp forces allow it to fill the mold without any gaps. However, LSR doesn’t need a lot of force because it already expands during the curing process due to the cross-linking method.
As opposed to other processes, LSR is different from organic rubber because it’s heat resistant, biologically inert, and has low-temperature flexibility. Liquid silicone rubber cures faster and has properties unobtainable with traditional forms. For example, latex doesn’t cure all the way which can lead to poor reactions between medical rubber products and patients in the medical realm.
Benefits of choosing LSR as a solution includes it not degrading until heated to extreme temperatures and being able to handle the sterilization process. You can combine several components at a time, and the process often involves aggressive undercuts. We will dive into the benefits further in the guide.
Using a closed-loop system to produce LSR products, SIMTEC can limit the product’s exposure to contaminants like dust and moisture. It creates a clean production site and also reduces waste and rework because one of our trained technician controllers can alter the flow of material for each project. No air touches the parts until we remove it from the mold which improves part quality.
A closed-loop system allows the machine to react to changes in viscosity along with air bubbles. We monitor the correct amount of material ratio using a helical gear flow meter which has gear teeth to measure the flow in increments for precise amounts. Data gets sent back to one of our operators who controls the valve and can alter the flow which creates the closed loop.
LSR cures fast which is critical for the medical industry, and the solutions won’t leak chemicals or cause potential reactions.Chapter 2: LSR 2-Shot & Overmolding Innovative Technology